Radioactive salts of alpha-sulfo fatty acids



3,32%,295 Patented May 16, 1967 ice Delaware No Drawing. Filed Mar. 3, 1965, Ser. No. 436,910

9 Claims. (Cl. 260429.ll)

This invention relates to novel and unique radioactive cations.

It is often desirable to separate cations, which may be harmful in themselves, or, at the other extreme, may be extremely valuable in themselves, from aqueous solutions wherein they are present. Thus certain cations are sometimes present in extremely minute amounts in various aqueous solutions wherein they have certain detrimental effects, either through coordination with certain biological organisms, or in conjunction with other chemicals. Other cations, which are valuable for certain purposes, are present in the earths crust in extremely dilute amounts, or they are extremely difficult to separate from other more abundant materials. The instant ivnention provides unique and unobvious radioactive cation salts and a method of obtaining such cations from aqueous solutions. These cations, in many instances, are useful per se, but may also be useful in conjunction with other divergent materials. The various cation salts, provided by the method of the instant invention, may be used to disperse the desired cations within a particular system to achieve a uniform and/or homogeneous composition so as to provide novel functions not heretofore appreciated for such cation salts. Of course, the cations provided by the method of the instant invention may be used as such in accordance with their known, or presupposed characteristics. Some of the cations provided by the instant invention are available through other methods, such as conventional mining, but these methods are generally not available where the desired cation is present only at extremely low concentrations. Further these methods normally involve numerous openations and relatively high cost. The instant invention provides a method of obtaining cations easily and economically, whereby the various cations are obtainable in a minimum number of operations and at substantial saving.

One of the essential features of the instant invention is therefore, to provide novel and unique radioactive cation salts having unique properties as dispersing agents, emulsifying agents, surfactants, etc., such that are useful per se and/or useful in conjunction with other diverse materials to provide marketable, uniform, homogeneous compositions having heretofore known or unknown utility including utility as industrial poisons, metallurgical agents, mutation agents, age determining agents, stabilizers, catalysts, explosives, tracers, or the like.

It will be appreciated that, although the novel radioactive cation salts provided by the method of the instant invention have certain common characteristics, properties, or utility relating to their emulsifiable or dispersible characteristics per se, they are also capable of diverse functions per se or in combination with other materials.

It is therefore an object of the instant invention to provide unique and unobvious radioactive cation salts.

Another object of the present invention is to provide a method of scavenging radioactive cations from aqueous solutions.

It is a further object of the instant invention to provide a radioactive cation salt formed by cations that are naturally radioactive and an alpha-sulfo fatty acid,

A still further object of the instant invention is to provide a method of separating :at least two different radioactive cations wherein predetermined increments of an acid is added to the aqueous system sequentially thus causing a successive precipitate to be formed and removing the same, then repeating successively such sequential addition of the predetermined increment of acid until no more precipitate is formed, whereby one of said radioactive cations is more concentrated in the initial precipitate than in the starting materials.

Other and further objects, features and advantages of the present invention wil become more apparent to those skilled in the art from the following detailed description thereof.

In its more general aspects, the instant invention consists of providing a unique and unobvious method of obtaining certain radioactive cation salts of alpha-sulfonic alkyl radicals; and in its more specific aspects, the instant invention consists in providing a method of obtaining cation salts of alpha-sulfonic C -C fatty acids which may be basic or neutralized. In general, the anion of the cation salt is prepared by the alpha-sulfonation of a fatty acid foundation having the following general formula:

wherein R is a C C- alkyl radical. The alkyl radical foundation (I) is either the acid per so at the time it is sulfonated, or may be an ester. The radical R in the acid (I) may be a typical C -C fatty acid residue, i.e., it is a fatty acid residue containing from 8 to 20 carbon atoms, so that the fatty acid foundation (I) is that of a C -C fatty acid. Such fatty acids include octanoic (capric), dodecanoic (lauric), tridecanoic, tetradecanoic (myristic), pentadecanoic, hexadecanoic (palmitic), heptadecanoic (margaric), octadecanoic (stearic), nonadecanoic, eicosanic (arachidic), hencicosanic and docosanic (behenic) acids. The acids preferred in the use of the instant invention are palmitic, stearic and arachidic, which make the radical R preferably a C -{l radical. The sulfo group replaces one of the hydrogen atoms on the alpha carbon of the fatty acid foundation (I) just described and this alpha-sulfonation may be carried out by sulfonating the fatty acid per so (with or without suitable solvents) or a salt of the fatty acids, also with or without suitable solvents) with a conventional sulfonating agent such as oleum, chlorosulfonic acid or sulfur trioxide (S0 Comparatively, the alpha-sulfonation may be carried out in the practice of the instant invention by sulfonation of a suitable ester of the fatty acid, such as methyl ester. If such an alternative route is used, upon obtaining the 'alpha-sulfo fatty acid ester one may carry out hydrolysis, if desired, to replace the methyl group with hydrogen, or with another ester group, which would then become a transesterification process.

The neutralization of the alpha-sulfonic acid group is a conventional procedure for neutralizing the sulfonic groups. It merely involves reaction with a suitable material providing a cation selected from the Periodic Chart of the Atoms such as actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, etc., or from other groups within the Periodic Chart as, for example, polinium, radium, astatine, etc. Since, however, many cations have a valence of more than one and such are also usable to neutralize the sulfonic acid group the symbol M may be used for simplifying the general scheme for preparing the compounds in this invention, but this symbol M is not suitable for actually defining the resulting salt. It will thus be appreciated that a salt of a polyvalent metal,

3 for example, the salt of radium nitrate base and alphasulfo stearic acid may be a mixture of:

S O sRaNOa Radium nitrate and alpha sulfo stearic acid are reacted in equimolar proportions the basic salt (II) will predominate, and if the amount of the acid is increased up to two mols, the neutralized salt (III) will tend to predominate; but the true chemical structure involved in a given instance is difficult to determine and doubtlessly includes mixtures which, depending on the reaction proportions, ingredients, and/or materials will act as (or will be functionally) a basic or neutralized salt that is alkaline-reacting.

The term cation as used in the instant invention refers to a positively charged atom which passes to the cathode or negative pole during electrolysis. Cations are those ions that carry the positive current in a cell and are deposited on the cathode. They travel in the nominal direction of the current. Normally such cations are atoms of a metal, however, certain elements tend to act as metals in one environment and as nonmetals in another environment but these may be referred to as cations. These types of elements have been sometimes referred to as transition elements.

Radioactivity may be defined as a phenomenon resulting from instability of the atomic nucleus in certain atoms whereby the nucleus experiences a spontaneous but measurably delayed nuclear transition or transformation with the resulting emission of radiation. The discovery of natural (as contrasted to man-made) radioactivity by H. Becquerel in 1896 was an indirect consequence of the discovery of X-rays a few month-s earlier by W. Rtintgen, and marked the birth of nuclear physics. The radiations resulting from the nuclear transitions were subsequently studied and found to consist of three distinct types. These were designated as u-rays (helium nuclei), p-rays (negative or positive electrons), and 'y-rays (high-frequency electromagnetic radiation).

In 1919 Lord Rutherford discovered that atomic nuclei could be broken up by bombardment with a-rays to form other nuclei. In 1934 Irene Curie and her husband Joliot first demonstrated that such artificially created nuclei themselves disintegrate spontaneously; this phenomenon is called artificial, or induced, radioactivity. A'll chemical elements may be rendered radioactive, and the availability of this wide variety of radioactive isotopes stimulated their use in science and technology in an enormous number of applications. The present invention is concerned only with those cations which are naturally radioactive.

A further aspect of the invention consists of separating various and diverse radioactive cations from an aqueous solution where they are present.

The so-called radioactive minerals loosely comprise species that contain uranium or thorium as an essential part of their chemical composition, together with minerals in which these elements are sometimes present in solid solution, usually in small and variable amounts. About 150 minerals fall into the first category, including many that are rare or that are imperfectly known. The principal uranium minerals from the point of view of their economic importance are the oxide uraninite and its variety pitchblende, the vanadates carnotite and tyuyamunite, the silicate coffinite, the phosphates autunite and torbernite, and the complex oxides brannerite and davidite. The chief thorium minerals of economic interest are the silicates thorite and thorogummite and the oxide thorianite.

The minerals that contain uranium or thoium in small amounts as vicarious constituents are relatively numerous. Some of them are of present or potential economic interest as sources of uranium or thoium, particularly when these elements can be obtained as by-products of the recovery of associated elements or minerals. The chief source of thorium in the past has been the rare-earth phosphate mineral monazite, which commonly contains thorium as a vicarious constituent in the range from 3 to 10% ThO Uranium often is an important accessory constituent in the niobate-tantalates, and is present sometimes in significant amounts in many other minerals including allanite, zircon, and the aptite of some phosphaterock deposits. Thorium occurs as an accessory constituent chiefly in minerals containing zirconium, cerium, calcium or uranium.

Many other radioactive cations besides uranium and thorium are present in these and other related types of minerals. The scarcity of these cations in the selected mineral makes the obtention of the pure cations undiluted by extraneous materials extremely difficult and expensive. The invention provides a relatively economical and easy method of separating and purifying the desired cation from its environment. The minerals containing the desired cations are placed in aqueous solution so that they are dissolved in the aqueous solution. Then the a-sulfo alkyl acid is added in predetermined increments causing the desired cation to form a salt with the a-sulfo acid and separate from solution as a precipitate.

It has further been found that where more than one desired cation is present in the aqueous solution it is possible to separate them. Thus when two desired cations have been precipitated from a common aqueous solution and it is desired to separate .the two cations, the precipitate is redissolved in an aqueous media. Small amounts of the OL-SLllfO acid are added causing proportionate amounts of a precipitate to be formed which is separated from the mother liquor. This procedure is repeated until no more precipitate is formed in the mother liquor. Through this fractional precipitation it has been found that the initial precipitates are more concentrated in one of the desired cations than in the starting material, thus allowing the separation of the desired cation.

It was also discovered that when an excess of the msulfo alkyl acid is added to an aqueous solution containing precipitated salts of the desired cations and the oc-SlllfO alkyl acid, certain of these precipitated cations are brought back into solution while others are relatively unaffected thereby. This has proven to be another useful method of separating the desired cation.

It will be seen from the following demonstrations that the acid is added in predetermined increments ranging from substantially l to 10% of the total concentration of cations. However, it was noted that all concentrations of naturally radioactive cations tested were precipitated. No actual theoretical minimum or maximum concentrations of naturally radioactive cations (other than the ability of the cation to enter into aqueous solution) were detected. Thus, it is possible to fully remove naturally radioactive cations from aqueous solution by .the addition of sufficient a-sulfo alkyl acid. It is, of course, recognized that the OL-Slll-fO alkyl .acid may be separated from the radioactive cation after it has been separated from the aqueous solution so as to leave the cation in a desired state and regenerate the a-sulfo alkyl acid for further use in precipitating radioactive cations still in solution.

Demonstrations The reagent (R) used throughout all the demonstrations is a stock solution of 0.01 .M in water and the reagent amount is aqueous 3' 10 molar, i.e., 0.03 cc. of stock solution (one drop).

(a) To 5 cc. of a 2.08 1'0 molar solution of Th(NO (1000 p.p.m. of cation in B 0) was added the reagent amount of R and an extremely heavy precipitate formed which was readily separated. In this, and all subsequent experiments, the only known chemicals present, except the water, were those specified so that it may be concluded that a Th salt of R was formed.

(b) To 5 cc. of a 2.08 X molar solution of Th (NO (10 p.p.m. of cation in H O) was added the reagent amount of R and a slight precipitate formed which was easily separated.

to) To 5 cc. of a l.31 l()- molar solution of U( NO (475 p.p.m. of cation in H O) was added the reagent amount of R and a whitish precipitate slowly formed which was separated quite readily.

To 5 cc. of a 3.06 10- molar solution of Sm( NO wherein R is an alkyl radical having from 8 .to carbon atoms, said cations being selected from the group of radioactive cations consisting of Sm, Ra, Fr, Po, Ac and the members of the actinium series having atomic weight of at least 230.

2. The Th salt of alpha-sulfo C C alkanoic acid.

3. The Th salt of alpha-sulfo stearic acid.

A salt of Sm and alpha-sulfa Cp -C2 alkanoic acid. A salt of Sm and alpha-sulfo stearic acid. A salt of U and alpha-sulfo (E -C alkanoic acid. A salt of U and alpha-sulfo stearic acid.

8. A method of precipitating radioactive cations from aqueous solution which comprises adding to said solution an amount of an oc-SlllfO fatty acid having the formula:

wherein R is an alkyl radical having from 820 carbon atoms, (2) thus causing a successive precipitate to be formed and removing the same, and then (3) repeating successively steps (1) and (2) and collecting the precipitate separated until no more precipitate is formed in step (1) whereby l of said radioactive cations is more concentrated in the initial precipitates than in the starting material.

References Cited by the Examiner UNITED STATES PATENTS 4/1963 Rinse 260429.3 8/1965 Sebba 260-4292 CARL D. QUARFORTH, Primary Examiner. S. I. LECHERT, JR., Assistant Examiner. 

1. A SALT OF A CATION AND AN ACID HAVING THE GENERAL FORMULA:
 8. A METHOD OF PRECIPITATING RADIOACTIVE CATIONS FROM AQUEOUS SOLUTION WHICH COMPRISES ADDING TO SAID SOLUTION AN AMOUNT OF AN A-SULFO FATTY ACID HAVING THE FORMULA: 